Aluminium workpieces are widely used as structural components in industrial construction, especially to replace heavier steel components. However, for some applications it is difficult to find aluminium workpieces which offer similar structural characteristics as according steel structures they are supposed to replace. Especially one-piece steel workpieces comprising sections with different material characteristics such as strength or ductility are difficult to replace with adequate aluminium workpieces.
For steel production there are known techniques in the art like for example press hardening, which allow manufacturing one-piece workpieces with sections of different material characteristics. These techniques exploit the high sensitivity of steel microstructure to the quenching rate in a hardening process as well as its low thermal conductivity. Due to these properties different parts of a steel workpiece can be exposed to very different temperature gradients during quenching to achieve different structure states with different material characteristics.
These methods are usually not applicable to aluminium workpieces as aluminium alloys have a higher thermal conductivity so that temperature differences between different parts of a workpiece are leveled out faster. Moreover, it is usually necessary to keep an aluminium workpiece at a specific temperature for an extended and defined time to achieve a specific structure state rather than only exposing the workpiece to a certain quenching rate.
In some cases it may be possible to replace a one-piece steel workpiece by a multiple-piece aluminium workpiece which is composed of at least two aluminium workpieces having different material characteristics which are joined together. The joining of workpieces by for example welding or soldering is however not always possible and also introduces weak points into the workpiece. Therefore there is a general need for one-piece aluminium workpieces with portions of different material characteristics.